Explaining Global Trends in Cattle Population Changes between 1961 and 2020 Directly Affecting Methane Emissions

Round 1

Reviewer 1 Report

I had the pleasure to be invited to review the manuscript "Explaining global trends in cattle population changes between 2 1961 and 2020 directly affecting methane emissions"

The general idea is good and looks coherent. However, based on the presented data there is no link between what was thought to be presented (inspiring it from the tile). There is no data on CH4 emission and its evolution through the studied period in the different selected countries. In such a case, emission factors should be taken into consideration because each zone/are use a proper EF to calculate CH4 emission. Moreover, the production system that directly affects the CH4 is not presented.  I suggest to add this missed data if not change the title, and the contents mentioning that the study is focused on the evolution of cattle population through the time (1961-2020) without focusing on CH4 emission. Abstract, Introduction, Discussion and conclusion would be hence changed according to the presneted data

Comments for author File: Comments.pdf

Minor revision for English language would be done. 

Author Response

Thank you very much for valuable comments in the review.

We have improved the manuscript including the comments. One of the most important complement in the manuscript is addition of methane emission connected with cattle (enteric methane emission and connected with manure storage and management). The methane emission which were added to the results are based on Tier 1 method and come from FAOSTAT database. Abstract, Introduction and Discussion were extended to present the link between cattle population and methane emission.

Author Response File: Author Response.pdf

Reviewer 2 Report

Interesting: when I started reading the introduction, I believed that the work would measure the levels of methane gas (CH4) produced by several sources, including cattle. However, the authors made an assessment of herd growth and tried to attribute the greenhouse effect problem to land use and livestock. Without measuring such effects efficiently for all variables, including these.

 

They begin the discussion by stating “-Our results therefore represent the lower bound of the actual contribution of live-300 stock systems to global warming as we rely solely on emissions that can be directly and 301 unambiguously attributed to livestock. 302”

But then they seem to discuss what they didn't compare. It would have been interesting if they had presented milk production by country; meat; CH4 production and correlated this with the other characteristics analyzed. I was surprised that they hold discussions of other articles. But their own information is not discussed. They must present milk production by country; meat; of CH4, population growth; and show % of food according to the source that the population of each country uses. And from there start the discussion and based on their results. They should compare with results from other authors. But it is essential that they build on what they have done. As this paper must be work.

 

Reconsider after major revision

 

Explaining global trends in cattle population changes between  1961 and 2020 directly affecting methane emissions

 

 Keywords: enteric fermentation; cattle population; agriculture; greenhouse gas emissions

 

There are repeated words in the title and keywords. You only need to choose one location.

The legend (Catle (mln??)heads) of Figure two is not clear. Need to adjust. The line of greed make confusion the writer)

 

Fig. 2.:- The caption (Cattle (mln???) heads) of Figure two is unclear. Need to adjust. The grid line confuses the reader) The graphic is polluted. Lots of writing. Authors must reduce the writing and place them in the footer. Decrease line thickness. And greed can be thinner too!

 

Need to define the acronyms. The authors use mln, however this is not defined anywhere in the paper.

 

Table 1 is out of text pattern (larger) - needs to be adjusted.

 

In Figure 4 the axes need to be identified.

 

Why is Chad out of alphabetical order in Table 1?

 

Figure 5: The authors must inform what the numbers below the name of the country are (growth or reduction of the herd in the studied period). This is relevant information that is loose in the figure.

 

 

Table 2: The top line is too long and confusing. Maybe insert acronyms and describe them in Footer. The table size is out of standard. Needs to be revised.

Country

Gro-up

Agricul-tural land

Farm ma-chinery

GDP per capita

Land un-der perm. meadows and pas-tures

Meat beef consump-tion per capita

Meat total (incl. fish and sea-food) con-sumption per capita

Milk consumption per capita

Milk yield per animal

Rural population percent

Total population

 

The correlation table is confusing. Perhaps the numbers should be written in black. It would improve the look.

The Red and Blue could be a milder hue in order to be smoother.

 

The table three is confuse too. Need adjust.

 

 

On line 224, the authors put Relation between the bovine population and other variables. But in the material and methods these variables need to be described and also how they were measured. This does not exist and as it is written it seems like an assumption. For a discussion, it will, but for a scientific work it is not acceptable. Is the material and method very superficial in terms of correlated characteristics? How were they measured? How were they obtained? What sources?? Ah, it was FAO, but where in the FAO? This must be well referenced. (Tables 2 and 3)

 

Gro-up

Agricul-tural land

Farm ma-chinery

GDP per capita

Land un-der perm. meadows and pas-tures

Meat beef consump-tion per capita

Meat total (incl. fish and sea-food) con-sumption per capita

Milk consumption per capita

Milk yield per animal

Rural population percent

Total population

 

 

CT

CT/AL

CT/TP

AL

FM

GDP

LMP

MBC

MTC

MC

MYA

RPP

TP

 

???

 

 

Where is this information (numbers, quantitative)? Where did they come from?? This must be shown. What sources??

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors

Thank you for submitting your article. The article is interesting and written very well. I have very few concerns about the methods and discussion.

The Materials and methods is not clear nor the descriptive. It should be written extensively with heading. There should be clear mentioning of variables and factors of the study. 

Discussion should avoid the redundancy of the data. A very formal discussion should be given that focus on the research question.

Minor editing is required.

Author Response

Thank you very much for valuable comments in the review. We have improved the manuscript according to the comments.

 

Reviewer 4 Report

This manuscript uses FAO data to show the change in cattle populations in the 30 countries with the largest populations. PCA and correlation is used to determine trends in cattle population growth for different groups of countries. Cattle population growth was forecast, and related to future methane emissions. Due to the contribution of cattle to methane emissions at the global scale, this work is highly relevant. The manuscript is clearly written with methods explained in detail, results well presented and discusssed.

 

Author Response

Thank you very much for the review. 

Round 2

Reviewer 1 Report

As a reviewer of the manuscript "Explaining global trends in cattle population changes between 2 1961 and 2020 directly affecting methane emissions" in its  second round  I belive that some points commented in the first round were taken into consideration by authors. However, still some unclearance exists in the different sections:

Introduction is very long and many times confusing. Material and Methods: is not too clear. Calculation/estimation of some parameters is not clear. Data issued from a database should be more explained on how it was calculated. Exp; the CH4 issued from cattle in different countries was not measured by the same technique/same emission factor. This is very important, because in such cases we can not justify that differences based on CH4 are related to cattle population , breed or else. The first factor is the EF used for calculation. Some countries use their own EF but generally developing countries use EF of other different countries. This issue should be highlighted and explained.  Cattle breeds in the different countries should be more highlighted, as CH4 emissions depend partly on the genetic breed of the animal species. Results section: it should contain the most relevant results without presenting explanation or discussion of what happened; Discussion: should be in coherent with the presented results  Conclusion: is not coherent with the most relevant results  I suggest that the manuscript can not be published under this form. Authors check all the comments and review different sections of the manuscrit. English should be reviewed by a speaker English   

The manuscript have to be reviewed by an english speaker

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors, the job received improvements. Tables must have numbers and characters in black, to facilitate visualization. Even if you highlight it in red and blue. Finally, you must show the paper, the production of CH4 by country and make a linear or multiple regression. Showing the relationship between cattle growth population and methane production.

The conclusion should be simple, robust, and straightforward. There is no need for results and goals (aim). Please highlight what was inserted in the paper

Only with these adjustments, the paper should be published.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

I suggested a minor revision, especially of the english in order to get more coherence between objective and conclusion. Alos I suggested changing the title (it should be reformulated) .

Some remarks have been done on this attached version. 

In conclusion, with a minor revision the paper could be accepted for publication and would get a great scientific sound.

   

 

 

Comments for author File: Comments.pdf

I suggested a minor revision, especially of the english in order to get more coherence between objective and conclusion. Alos I suggested changing the title (it should be reformulated) .

Some remarks have been done on this attached version. 

In conclusion, with a minor revision the paper could be accepted for publication and would get a great scientific sound.

Author Response

Thank you very much for all the previous comments and a positive opinion about the article.
As suggested, we tried to improve the title of the article. Our suggestion is "Explaining Global Trends in Cattle Population Changes between 1961 and 2020 and the Associated Methane Emissions". However, we are afraid that it does not sound better than the title that has been so far.
Emission is indeed repeated twice, but this follows from the description of the mathematical formula:
“emission = emission factor × number of cattle”
We reformulated the sentence:
“…the countries with the highest cattle population make the highest contribution to methane emissions”
into 
“…the countries with the highest cattle population are the primary contributors to methane emissions from agricultural sources”
We removed the sentence:
“This analysis will provide an estimate of the livestock systems' contribution to global warming.”
Finally, we read the article carefully to get greater coherence between objective and conclusions and correct the language errors. Furthermore, some formatting changes were done. We very much hope that we have been able to improve the manuscript.

Reviewer 2 Report

Ok,  publish the paper.

Author Response

Thank you very much for all the previous comments and the positive opinion about the article.